Solutions of rubbery polymers from particles of uniform diameter



Patented Feb. 10, 1953 SOLUTIONS OF RUBBERY POLYMERS FROM PARTICLES F UNIFORM DIAMETER Carll F. Van Gilder, Roselle, and William C. Harney, Elizabeth, N. J assignors to Standard Oil Development Co Delaware mpany, a. corporation of No Drawing; Application September 9, 1949, Serial No. 114,904

3 Claims. (01. 260-285.)

This invention relates to solutions of high molecular weight polymers and more particularly to the production of solutions of high polymer content which are homogeneous and lump free.

Dilute solutions of rubbery polymers are usually prepared by stirring the polymer into solvents such as ether, benzene, carbon tetrachloride, carbon disulfide, naphtha, oils, waxes, and the like, until a homogeneous solution is obtained. Such solutions eldom contain more than 1% of polymer.

In many cases it is desirable to obtain the maximum possible polymer content consistent with a viscosity which will permit satisfactory use of the solution. In order that a large amount of polymer may be incorporated into a given solvent, it has been necessary to subject the polymer to a long and sometimes severe milling operation or to mastication with heavy duty direct action mixing equipment, such as kneaders, banburys, or extruders. Excessive milling is sometimes extremely harmful to the polymer, tending to break it down so that the final product is of very inferior quality and much of its desirable qualities are lost. Furthermore, heavy equipment is expensive initially, the power requirements are largeand general batch sizes are limited, all of which result in increased blending costs.

A characteristic property of rubbery polymers is that they swell gradually in the solvent which penetrates the aggregate from the surface into the center at which point the polymer is completely dispersed. However, as the solvent viscosity increases the rate of solvent penetration decreases to such an extent 'that some or the large particles of the aggregate are not completely attached and the final blend contains lumps ofpartially swollen polymer or fish eyes" I and the blend is not homogeneous. In preparing blends of high molecular weight polymer wherein cosities involved, it is not feasible to. filter orstrain the blends to remove the lumps. Accordingly, for blends above 5000 centistokes positive action mixing equipment is required.

According to the present invention, it has been found that if the size of the polymerparticles.

which are being dissolved are maintained'uniform and below inch in diameter, preferably at about t; inchi m inch, that high viscosity.

blends which are homogeneous and lump-free can be obtained by simple agitation.

The desired polymer particle sizes which are useful according to the present invention can be obtained in any manner known to the art. However, it has been found that extrusion through a nozzle having a bore of the desired diameter and provided with a slicer adaptedto out 01f pellets of uniform size is a particularly desirable method of obtaining particles of uniform size.

The following table gives data showing the advantages of the use of small uniform particle sizes of the present invention over larger sizes and non-uniform crumb particles when dissolved in parafiln wax melting at 132 F.

TABLE 1 Solution rates of polyisobutylene in wax 132 F.

M. P. at 230 F.

[10- polymer-% wax.1

Type M0 in. Pellets, }i0ln.Pel1ets 940 in.Pellets.. Crumb Crumb.

PERCENT POLYMER DISSOLVED AT HRS.-

From the above data it is apparent that the 1*; inch pellets dissolved many times faster than the inch pellets and reached a maximum concentration of within five hours whereas after 48 hours only 4.4% of the inch polymer 5 was dissolved. Thecrumb polymer. dissolved somewhat" faster 'thanthe 5 inch." pellets due to the fact that the crumb contained many mall particles, yet only 9.3% was dissolved after 65- hours. Furthermore, the resulting solution from 1 the crumb polymer was lumpy while that from the inch pellets was homogeneous.

As a further illustration data .1 are given in Table 2 showing the viscosityof solutionsiprepared at various polymer contents of pelletized 94,000 molecular weight polyisobutylene in 132 F. M. P. wax.

TABLE 2 Solution rate of polyisobutylene pellets 94,000 M. W. in 132 F. M. P. wax" [Solution Temp 130-150- 0.]

Percent Polymer Tiine,.Hrs. 5??? Remarks;

1 s43 Lump l' '1 257. Slightly Lumpy: 3%- 238 No lumps... 2% 144' 1 Do;

1 After dilution of'blend '1 partwith 3 parts ofwa'xr The-aboverdata show that up to. -16 polymer can berdissolvedin wax--ini3% hours to givealump-free solution havinga viscosity of better than 40,000 centistokesp at 210- F. before dim-- 5 tion which represents a saving1in polymer. of 10-- 20%" over that necessary to. produce equivalent viscosity by positive action equipment.

The process of the present invention may be. appliedrtoiany type'ofrubbery polymer which it 0 is desired to dissolve,includingynatural rubber, the various synthetic rubbers, Buna-S (the copolymer of butadiene: and styrene), Perbunan (the copolymer of butadiene and acrylonitrile) polyisobutylene, Butyl rubber (the copolymerof isobutylene. and butadiene or= isoprene), polyethylene and the liken With the detailed disclosure-above given, it is. obvious that modifications will suggest themselves, for instance, other solvents than those listed may be used, also various compounding or filling substances, accelerators, antioxidants, and the like, without departing from the principle of the invention.

The solutions produced in accordance with this invention are useful for'many. purposes such as adhesives, impregnating materials, dipping or spreading cements, binders when mixed with wood flour, cork, etc. They are useful as waterproofing" materials,- coating compositions, and thelike;

The nature and objects of the present inventionhavingthusbeen set forth and specific examplesuof the same given, what is claimed as new and useful anddesired to be secured by Letters Patent is:

1'. A'= process for preparing solutions of high molecular weight rubbery polymers in wax which .comprises agitating with the wax, at a temperature above the melting point of the wax, polymer. particlesselected from. thegroup of rubbery polymers consisting of naturalrubber, the copolymer. of butadiene and styrene, the copolymer of butadiene and acrylonitrile, polyisobutylene, polyethylene, and'the copolymer of isobutylene and a diolefin selected from the group consisting of butadiene and isoprene, ,saidrpolymer particles being of uniform size of not over /4. inch diameter.

2.. A. process for. preparing. solutions of "poly isobutylene in wax whichicomprises agitating polyisobutylene particles having a uniform diameter. not over /4 inch with the wax at a temperature. above the melting point of the wax.

3. Process. according to claim 2 in which the polyisobutylene-particles .are. uniformly 1% inch.

in diameter.

CARLL' F, VAN GILDER.. WILLIAM C. HARNEY.

REFERENCES CITED The following references are of recordrinthe file of this patent:

UNITED STATES PATENTS Number I Name Date 2,227,516 Soanes Jan. '7, 1941! 2,404,713 Houtz July 23;}1946' 

1. A PROCESS FOR PREPARING SOLUTION OF HIGH MOLECULAR WEIGHT RUBBERY POLYMERS IN WAX WHICH COMPRISES AGITATING WITH THE WAX, AT A TEMPERATURE ABOVE THE MELTING POINT OF THE WAX, POLYMER PARTICLES SELECTED FROM THE GROUP OF RUBBERY POLYMERS CONSISTING OF NATURAL RUBBER, THE COPOLYMER OF BUTADIENE AND STYRENE, THE COPOLYMER OF BUTADIENE AND ACRYLONITRILE, POLYISOBUTYLENE, POLYETHYLENE, AND THE COPOLYMER OF ISOBUTYLENE AND A DIOLEFIN SELECTED FROM THE GROUP CONSISTING OF BUTADIENE AND ISOPRENE, SAID POLYMER PARTICLES BEING OF UNIFORM SIZE OF NOT OVER 1/4 INCH DIAMETER. 